"disable_script" function breaks "grub-mkconfig"

* "disable_script" function breaks "grub-mkconfig":
  * Replace "return 1" by "exit 0".

41_snapshots-btrfs

@@ -1,38 +1,33 @@
 #! /usr/bin/env bash
 #
-#
 # Written by: Antynea
 # BTC donation address: 1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt
 # Github: https://github.com/Antynea/grub-btrfs
 #
 # Purpose:
 #   Improves Grub by adding "btrfs snapshots" to the Grub menu.
-#   You can start your system on a "snapshot" from the Grub menu.
-#   Supports manual snapshots, snapper ...
-#   Warning : booting on read-only snapshots can be tricky
+#   You can boot your system on a "snapshot" from the Grub menu.
+#   Supports manual snapshots, snapper, timeshift ...
+#   Warning : booting on read-only snapshots can be tricky.
 #   (Read about it, https://github.com/Antynea/grub-btrfs#warning-booting-on-read-only-snapshots-can-be-tricky)
 #
 # What this script does:
 # - Automatically List snapshots existing on root partition (btrfs).
 # - Automatically Detect if "/boot" is in separate partition.
-# - Automatically Detect kernel, initramfs and intel microcode in "/boot" directory on snapshots.
-# - Automatically Create corresponding "menuentry" in grub.cfg
+# - Automatically Detect kernel, initramfs and intel/amd microcode in "/boot" directory on snapshots.
+# - Automatically Create corresponding "menuentry" in grub.cfg.
 # - Automatically detect snapper and use snapper's snapshot description if available.
 # - Automatically generate grub.cfg if you use the provided systemd service.
 #
 # Installation:
-# - Run `make install` or look into Makefile for instructions on where to put each file.
+# - Refer to https://github.com/Antynea/grub-btrfs#installation-
 #
 # Customization:
-#  Refer to config for the list of available options and their default values.
-#  Place your configurations to /etc/default/grub-btrfs/config.
+#  You have the possibility to modify many parameters in /etc/default/grub-btrfs/config.
 #
 # Automatically update Grub
-#  If you would like Grub to automatically update when a snapshots is made or deleted:
-#  - Use systemctl start/enable grub-btrfs.path
-#  - grub-btrfs.path automatically (re)generates grub.cfg when a modification appears in /.snapshots folder (by default).
-#  - If your snapshots aren't mounted in /.snapshots, you must modify the watch folder using systemctl edit grub-btrfs.path
-#  - See https://github.com/Antynea/grub-btrfs#automatically-update-grub
+#  If you would like grub-btrfs menu to automatically update when a snapshot is created or deleted:
+#  - Refer to https://github.com/Antynea/grub-btrfs#automatically-update-grub.
 #
 # Special thanks for assistance and contributions:
 # - My friends
@@ -41,25 +36,31 @@
 
 set -e
 
-prefix="/usr"
-exec_prefix="/usr"
 datarootdir="/usr/share"
 sysconfdir="/etc"
 grub_btrfs_config="${sysconfdir}/default/grub-btrfs/config"
 
 [[ -f "$grub_btrfs_config" ]] && . "$grub_btrfs_config"
-. "$datarootdir/grub/grub-mkconfig_lib"
-. "${sysconfdir}/default/grub"
+[[ -f "${sysconfdir}/default/grub" ]] && . "${sysconfdir}/default/grub"
+
+## Exit the script, if:
+disable_script() {
+    [[ "${GRUB_BTRFS_DISABLE:-"false"}" == "true" ]] && exit 0 # Disable Grub-btrfs is set to true (default=false)
+    if ! type btrfs >/dev/null 2>&1; then exit 0; fi # btrfs-progs isn't installed
+    [[ -f "$datarootdir/grub/grub-mkconfig_lib" ]] && . "$datarootdir/grub/grub-mkconfig_lib" || exit 0 # grub-mkconfig_lib couldn't be found
+    # Root filesystem isn't btrfs
+    root_fs=$(${grub_probe} --target="fs" / 2>/dev/null)
+    [[ "$root_fs" != "btrfs" ]] && exit 0
+    return 0
+}
+disable_script
 
-### Variables in /etc/default/grub-btrfs/config
-## Disable Grub-btrfs (default=active)
-[[ "${GRUB_BTRFS_DISABLE:-"false"}" == "true" ]] && exit 0
 ## Submenu name
 distro=$(awk -F "=" '/^NAME=/ {gsub(/"/, "", $2); print $2}' /etc/os-release)
 submenuname=${GRUB_BTRFS_SUBMENUNAME:-"${distro:-Linux} snapshots"}
 ## Prefix entry
 prefixentry=${GRUB_BTRFS_PREFIXENTRY:-"Snapshot:"}
-## Limit snapshots to show in the Grub menu
+## Limit snapshots to show in the Grub menu (default=50)
 limit_snap_show="${GRUB_BTRFS_LIMIT:-50}"
 ## How to sort snapshots list
 btrfssubvolsort=(--sort="${GRUB_BTRFS_SUBVOLUME_SORT:-"-rootid"}")
@@ -76,31 +77,24 @@ case "${GRUB_BTRFS_DISABLE_PROTECTION_SUBMENU:-"false"}" in
     *)      unrestricted_access_submenu=""
 esac
 # Authorized users (--users foo,bar)
-if [ ! -z "${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS}" ] ; then
+if [ -n "${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS}" ] ; then
     protection_authorized_users="--users ${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS} "
 fi
 
-### variables script
-## Probe info "Boot partition"
-# Boot device
-boot_device=$(${grub_probe} --target=device ${boot_directory})
-# hints string
-boot_hs=$(${grub_probe} --device ${boot_device} --target="hints_string" 2>/dev/null)
-# UUID of the boot partition
-boot_uuid=$(${grub_probe} --device ${boot_device} --target="fs_uuid" 2>/dev/null)
-# Type filesystem of boot partition
-boot_fs=$(${grub_probe} --device ${boot_device} --target="fs" 2>/dev/null)
-## Probe info "Root partition"
-# Type filesystem of root partition
-root_fs=$(${grub_probe} --target="fs" / 2>/dev/null)
-# Root device
-root_device=$(${grub_probe} --target=device /)
-# UUID of the root partition
-root_uuid=$(${grub_probe} --device ${root_device} --target="fs_uuid" 2>/dev/null)
+## Probe informations of Root and Boot devices
+# Probe info "Root partition"
+root_device=$(${grub_probe} --target=device /) # Root device
+root_uuid=$(${grub_probe} --device ${root_device} --target="fs_uuid" 2>/dev/null) # UUID of the root device
+# Probe info "Boot partition"
+boot_device=$(${grub_probe} --target=device ${boot_directory}) # Boot device
+boot_uuid=$(${grub_probe} --device ${boot_device} --target="fs_uuid" 2>/dev/null) # UUID of the boot device
+boot_hs=$(${grub_probe} --device ${boot_device} --target="hints_string" 2>/dev/null) # hints string
+boot_fs=$(${grub_probe} --device ${boot_device} --target="fs" 2>/dev/null) # Type filesystem of boot device
+
 ## Parameters passed to the kernel
 kernel_parameters="$GRUB_CMDLINE_LINUX $GRUB_CMDLINE_LINUX_DEFAULT"
 ## Mount point location
-gbgmp=$(mktemp -d)
+gbgmp=$(mktemp -dt grub-btrfs.XXXXXXXXXX)
 ## Class for theme
 CLASS="--class snapshots --class gnu-linux --class gnu --class os"
 ## save IFS
@@ -122,32 +116,54 @@ detect_rootflags()
                         | sed -E 's/^.*[[:space:]]([[:graph:]]+)$/\1/;s/,?subvol(id)?=[^,$]+//g;s/^,//')
     rootflags="rootflags=${fstabflags:+$fstabflags,}${GRUB_BTRFS_ROOTFLAGS:+$GRUB_BTRFS_ROOTFLAGS,}"
 }
+## Path to grub-script-check
+grub_script_check="${bindir}/grub-script-check"
 
-### Error Handling
+## Error Handling
 print_error()
 {
-    local arg="$@"
-    local nothing_to_do="If you think an error has occurred , please file a bug report at \" https://github.com/Antynea/grub-btrfs \"\nNothing to do. Abort.\n"
-    printf "${arg}\n${nothing_to_do}" >&2 ;
+    local err_msg="$*"
+    local bug_report="If you think an error has occurred , please file a bug report at \" https://github.com/Antynea/grub-btrfs \""
+    printf "%s\n" "${err_msg}" "${bug_report}" >&2 ;
     exit 0
 }
 
-test_btrfs()
+unmount_gbgmp()
 {
-    [[ "$root_fs" != "btrfs" ]] && print_error "Root partition isn't a btrfs filesystem.\nThis script only supports snapshots of the btrfs filesystem."
-    set +e
-    type btrfs >/dev/null 2>&1
-    if [[ $? -ne 0 ]]; then
-        print_error "Unable to retrieve info from btrfs filesystem, make sure you have btrfs-progs on your system."
+if [[ -d "$gbgmp" ]]; then
+    local wait=true
+    local wait_max=0
+    printf "Unmount %s .." "$gbgmp" >&2;
+    while $wait; do
+        if grep -qs "$gbgmp" /proc/mounts; then
+            wait_max=$((1+$wait_max))
+            if umount "$gbgmp" >/dev/null 2>&1; then
+                wait=false # umount successful
+                printf " Success\n" >&2;
+            elif [[ $wait_max = 10 ]]; then 
+                printf "\nWarning: Unable to unmount %s in %s\n" "$root_device" "$gbgmp" >&2;
+                break;
+            else
+                printf "." >&2 ; # output to show that the script is alive
+                sleep 2 # wait 2 seconds before retry
+            fi
+        else
+            wait=false # not mounted
+            printf " Success\n" >&2;
+        fi
+    done
+    if [[ "$wait" != true ]]; then
+        if ! rm -d "$gbgmp" >/dev/null 2>&1; then
+            printf "Unable to delete %s: Device or ressource is busy\n" "$gbgmp" >&2;
+        fi
     fi
-    set -e
+fi
 }
 
-### Script
 ## Create entry
 entry()
 {
-echo "$@" >> "$grub_directory/grub-btrfs.cfg"
+echo "$@" >> "$grub_directory/grub-btrfs.new"
 }
 
 ## menu entries
@@ -160,24 +176,25 @@ make_menu_entries()
         [[ ! -f "${boot_dir}"/"${k}" ]] && continue;
         kversion=${k#*"-"}
         for i in "${name_initramfs[@]}"; do
-            prefix_i=${i%%"-"*}
-            suffix_i=${i#*"-"}
-            alt_suffix_i=${i##*"-"}
-            if   [ "${kversion}" = "${suffix_i}" ];                 then i="${i}";
-            elif [ "${kversion}.img" = "${suffix_i}" ];             then i="${i}";
-            elif [ "${kversion}-fallback.img" = "${suffix_i}" ];    then i="${i}";
-            elif [ "${kversion}.gz" = "${suffix_i}" ];              then i="${i}";
-            else continue ;
-            fi
-            for u in "${name_microcode[@]}"; do
-                if [[ "${name_microcode}" != "x" ]] ; then
+            if [[ "${name_initramfs}" != "x" ]] ; then
+                prefix_i=${i%%"-"*}
+                suffix_i=${i#*"-"}
+                alt_suffix_i=${i##*"-"}
+                if   [ "${kversion}" = "${suffix_i}" ];                 then i="${i}";
+                elif [ "${kversion}.img" = "${suffix_i}" ];             then i="${i}";
+                elif [ "${kversion}-fallback.img" = "${suffix_i}" ];    then i="${i}";
+                elif [ "${kversion}.gz" = "${suffix_i}" ];              then i="${i}";
+                else continue;
+                fi
+                for u in "${name_microcode[@]}"; do
+                    if [[ "${name_microcode}" != "x" ]] ; then
                     entry "
     menuentry '"${k}" & "${i}" & "${u}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
-                else
+                    else
                     entry "
     menuentry '"${k}" & "${i}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
-                fi
-                entry "\
+                    fi
+                    entry "\
         if [ x\$feature_all_video_module = xy ]; then
         insmod all_video
         fi
@@ -191,18 +208,50 @@ make_menu_entries()
         echo 'Loading Snapshot: "${snap_date_time}" "${snap_dir_name}"'
         echo 'Loading Kernel: "${k}" ...'
         linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" ${kernel_parameters} ${rootflags}subvol=\""${snap_dir_name}"\""
-                if [[ "${name_microcode}" != "x" ]] ; then
-                    entry "\
+                    if [[ "${name_microcode}" != "x" ]] ; then
+                        entry "\
         echo 'Loading Microcode & Initramfs: "${u}" "${i}" ...'
         initrd \"${boot_dir_root_grub}/"${u}"\" \"${boot_dir_root_grub}/"${i}"\""
-                else
-                    entry "\
+                    else
+                        entry "\
         echo 'Loading Initramfs: "${i}" ...'
         initrd \"${boot_dir_root_grub}/"${i}"\""
-                fi
-                entry "    }"
-                count_warning_menuentries=$((1+$count_warning_menuentries))
-            done
+                    fi
+                    entry "    }"
+                    count_warning_menuentries=$((1+$count_warning_menuentries))
+                done
+            else 
+                for u in "${name_microcode[@]}"; do
+                    if [[ "${name_microcode}" != "x" ]] ; then
+                    entry "
+    menuentry '"${k}" & "${u}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
+                    else
+                    entry "
+    menuentry '"${k}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
+                    fi
+                    entry "\
+        if [ x\$feature_all_video_module = xy ]; then
+        insmod all_video
+        fi
+        set gfxpayload=keep
+        insmod ${boot_fs}
+        if [ x\$feature_platform_search_hint = xy ]; then
+            search --no-floppy --fs-uuid  --set=root ${boot_hs} ${boot_uuid}
+        else
+            search --no-floppy --fs-uuid  --set=root ${boot_uuid}
+        fi
+        echo 'Loading Snapshot: "${snap_date_time}" "${snap_dir_name}"'
+        echo 'Loading Kernel: "${k}" ...'
+        linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" ${kernel_parameters} ${rootflags}subvol=\""${snap_dir_name}"\""
+                    if [[ "${name_microcode}" != "x" ]] ; then
+                        entry "\
+        echo 'Loading Microcode: "${u}" ...'
+        initrd \"${boot_dir_root_grub}/"${u}"\""
+                    fi
+                    entry "    }"
+                    count_warning_menuentries=$((1+$count_warning_menuentries))
+                done
+            fi
         done
     done
     entry  "}"
@@ -220,17 +269,16 @@ trim() {
 snapshot_list()
 {
     # Query info from snapper if it is installed
-    type snapper >/dev/null 2>&1
-    if [ $? -eq 0 ]; then
+    if type snapper >/dev/null 2>&1; then
         if [ -s "/etc/snapper/configs/$snapper_config" ]; then
-            printf "Info: snapper detected, using config '$snapper_config'\n" >&2
+            printf "Info: snapper detected, using config: %s\n" "$snapper_config" >&2
             local snapper_ids=($(snapper --no-dbus -t 0 -c "$snapper_config" list --disable-used-space | tail -n +3 | cut -d'|' -f 1))
             local snapper_types=($(snapper --no-dbus -t 0 -c "$snapper_config" list --disable-used-space | tail -n +3 | cut -d'|' -f 2))
 
             IFS=$'\n'
             local snapper_descriptions=($(snapper --no-dbus -t 0 -c "$snapper_config" list --disable-used-space | tail -n +3 | rev | cut -d'|' -f 2 | rev))
         else
-            printf "Warning: snapper detected but config '$snapper_config' does not exist\n" >&2
+            printf "Warning: snapper detected but config: %s does not exist\n" "$snapper_config" >&2
         fi
     fi
 
@@ -250,12 +298,12 @@ snapshot_list()
         [[ ${snap_path_name%%"/"*} == "<FS_TREE>" ]] && snap_path_name=${snap_path_name#*"/"}
 
         # ignore specific path during run "grub-mkconfig"
-        if [ ! -z "${GRUB_BTRFS_IGNORE_SPECIFIC_PATH}" ] ; then
+        if [ -n "${GRUB_BTRFS_IGNORE_SPECIFIC_PATH}" ] ; then
             for isp in ${GRUB_BTRFS_IGNORE_SPECIFIC_PATH[@]} ; do
                 [[ "${snap_path_name}" == "${isp}" ]] && continue 2;
             done
         fi
-        if [ ! -z "${GRUB_BTRFS_IGNORE_PREFIX_PATH}" ] ; then
+        if [ -n "${GRUB_BTRFS_IGNORE_PREFIX_PATH}" ] ; then
             for isp in ${GRUB_BTRFS_IGNORE_PREFIX_PATH[@]} ; do
                 [[ "${snap_path_name}" == "${isp}"/* ]] && continue 2;
             done
@@ -300,6 +348,18 @@ snapshot_list()
             if [[ "$snapper_id" == "$id" ]]; then
                 local snapper_type=$(trim "${snapper_types[$j]}")
                 local snapper_description=$(trim "${snapper_descriptions[$j]}")
+                
+                # ignore snapper_type or snapper_description during run "grub-mkconfig"
+                if [ -n "${GRUB_BTRFS_IGNORE_SNAPPER_TYPE}" ] ; then
+                    for ist in ${GRUB_BTRFS_IGNORE_SNAPPER_TYPE[@]} ; do
+                        [[ "${snapper_type}" == "${ist}" ]] && continue 3;
+                    done
+                fi
+                if [ -n "${GRUB_BTRFS_IGNORE_SNAPPER_DESCRIPTION}" ] ; then
+                    for isd in ${GRUB_BTRFS_IGNORE_SNAPPER_DESCRIPTION[@]} ; do
+                        [[ "${snapper_description}" == "${isd}" ]] && continue 3;
+                    done
+                fi
                 printf -v entry "%-${max_entry_length}s | %-${max_type_length}s | %s" "$entry" "$snapper_type" "$snapper_description"
                 break
             fi
@@ -323,7 +383,7 @@ detect_kernel()
     done
 
     # Custom name kernel in GRUB_BTRFS_NKERNEL
-    if [ ! -z "${GRUB_BTRFS_NKERNEL}" ] ; then
+    if [ -n "${GRUB_BTRFS_NKERNEL}" ] ; then
         for ckernel in "${boot_dir}/${GRUB_BTRFS_NKERNEL[@]}" ; do
             [[ ! -f "${ckernel}" ]] && continue;
             list_kernel+=("$ckernel")
@@ -346,12 +406,13 @@ detect_initramfs()
     done
 
     # Custom name initramfs in GRUB_BTRFS_NINIT
-    if [ ! -z "${GRUB_BTRFS_NINIT}" ] ; then
+    if [ -n "${GRUB_BTRFS_NINIT}" ] ; then
         for cinitramfs in "${boot_dir}/${GRUB_BTRFS_NINIT[@]}" ; do
             [[ ! -f "${cinitramfs}" ]] && continue;
             list_initramfs+=("$cinitramfs")
         done
     fi
+    if [ -z "${list_initramfs}" ]; then list_initramfs=(x); fi
 }
 
 ## Detect microcode in "/boot"
@@ -371,7 +432,7 @@ detect_microcode()
     done
 
     # Custom name microcode in GRUB_BTRFS_CUSTOM_MICROCODE
-    if [ ! -z "${GRUB_BTRFS_CUSTOM_MICROCODE}" ] ; then
+    if [ -n "${GRUB_BTRFS_CUSTOM_MICROCODE}" ] ; then
         for cucode in "${boot_dir}/${GRUB_BTRFS_CUSTOM_MICROCODE[@]}" ; do
             [[ ! -f "${cucode}" ]] && continue
             list_ucode+=("$cucode")
@@ -428,7 +489,6 @@ boot_bounded()
         detect_rootflags
         # Initramfs (Original + custom initramfs)
         detect_initramfs
-        if [ -z "${list_initramfs}" ]; then continue; fi
         name_initramfs=("${list_initramfs[@]##*"/"}")
         # microcode (auto-detect + custom microcode)
         detect_microcode
@@ -448,11 +508,10 @@ boot_bounded()
         ### Limit snapshots found during run "grub-mkconfig"
         count_limit_snap=$((1+$count_limit_snap))
         [[ $count_limit_snap -ge $limit_snap_show ]] && break;
-        # Limit generation of menuentries if exceeds 250
-        # [[ $count_warning_menuentries -ge 250 ]] && break;
     done
     IFS=$oldIFS
 }
+
 boot_separate()
 {
     boot_dir="${boot_directory}"
@@ -465,7 +524,6 @@ boot_separate()
     name_kernel=("${list_kernel[@]##*"/"}")
     # Initramfs (Original + custom initramfs)
     detect_initramfs
-    if [ -z "${list_initramfs}" ]; then print_error "Initramfs not found."; fi
     name_initramfs=("${list_initramfs[@]##*"/"}")
     # microcode (auto-detect + custom microcode)
     detect_microcode
@@ -496,22 +554,17 @@ boot_separate()
         # Limit snapshots found during run "grub-mkconfig"
         count_limit_snap=$((1+$count_limit_snap))
         [[ $count_limit_snap -ge $limit_snap_show ]] && break;
-        # Limit generation of menuentries if exceeds 250
-        # [[ $count_warning_menuentries -ge 250 ]] && break;
     done
     IFS=$oldIFS
 }
 
-### Start
 printf "Detecting snapshots ...\n" >&2 ;
-# Only support btrfs snapshots
-test_btrfs
-# Delete existing config
-#rm -f --preserve-root "$grub_directory/grub-btrfs.cfg"
-> "$grub_directory/grub-btrfs.cfg"
+rm -f "$grub_directory/grub-btrfs.new"
+> "$grub_directory/grub-btrfs.new"
 # Create mount point then mounting
-[[ ! -d $gbgmp ]] && mkdir -p $gbgmp
-mount -o subvolid=5 /dev/disk/by-uuid/$root_uuid $gbgmp/
+[[ ! -d $gbgmp ]] && mkdir -p "$gbgmp"
+mount -o ro,subvolid=5 /dev/disk/by-uuid/"$root_uuid" "$gbgmp/"
+trap "unmount_gbgmp" EXIT # unmounting mount point on EXIT signal
 # Count menuentries
 count_warning_menuentries=0
 # Count snapshots
@@ -531,23 +584,25 @@ else
         boot_bounded
     fi
 fi
-# unmounting mount point
-umount $gbgmp
 # Show warn, menuentries exceeds 250 entries
-[[ $count_warning_menuentries -ge 250 ]] && printf "Generated ${count_warning_menuentries} total GRUB entries. You might experience issues loading snapshots menu in GRUB.\n" >&2 ;
-# printf "menuentries = $count_warning_menuentries \n" >&2 ;
+[[ $count_warning_menuentries -ge 250 ]] && printf "Generated %s total GRUB entries. You might experience issues loading snapshots menu in GRUB.\n" "${count_warning_menuentries}" >&2 ;
 # Show total found snapshots
-if [[ "${GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND:-"true"}" = "true" && ! -z "${count_limit_snap}" && "${count_limit_snap}" != "0" ]]; then
-    printf "Found ${count_limit_snap} snapshot(s)\n" >&2 ;
+if [[ "${GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND:-"true"}" = "true" && -n "${count_limit_snap}" && "${count_limit_snap}" != "0" ]]; then
+    printf "Found %s snapshot(s)\n" "${count_limit_snap}" >&2 ;
 fi
 # if no snapshot found, exit
 if [[ "${count_limit_snap}" = "0" || -z "${count_limit_snap}" ]]; then
     print_error "No snapshots found."
 fi
-# Make a submenu in GRUB (grub.cfg)
-cat << EOF
+# Make a submenu in GRUB (grub.cfg) and move "grub-btrfs.new" to "grub-btrfs.cfg"
+if ${grub_script_check} "$grub_directory/grub-btrfs.new"; then
+    cat "$grub_directory/grub-btrfs.new" > "$grub_directory/grub-btrfs.cfg"
+    rm -f "$grub_directory/grub-btrfs.new"
+    cat << EOF
 submenu '${submenuname}' ${protection_authorized_users}${unrestricted_access_submenu}{
     configfile "\${prefix}/grub-btrfs.cfg"
 }
 EOF
-### End
+else
+    print_error "Syntax errors are detected in generated grub-btrfs.cfg file."
+fi

Makefile

@@ -9,6 +9,10 @@ LIB_DIR = $(DESTDIR)$(PREFIX)/lib
 .PHONY: install uninstall help
 
 install:
+	@if test "$(shell id -u)" != 0; then \
+		echo "You are not root, run this target as root please."; \
+		exit 1; \
+	fi
 	@install -Dm755 -t "$(DESTDIR)/etc/grub.d/" 41_snapshots-btrfs
 	@install -Dm644 -t "$(DESTDIR)/etc/default/grub-btrfs/" config
 	@install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.service
@@ -23,6 +27,10 @@ install:
 	@install -Dm644 "initramfs/readme.md" "$(SHARE_DIR)/doc/$(PKGNAME)/initramfs-overlayfs.md"
 
 uninstall:
+	@if test "$(shell id -u)" != 0; then \
+		echo "You are not root, run this target as root please."; \
+		exit 1; \
+	fi
 	@grub_dirname="$$(grep -oP '^[[:space:]]*GRUB_BTRFS_GRUB_DIRNAME=\K.*' "$(DESTDIR)/etc/default/grub-btrfs/config" | sed "s|\s*#.*||;s|(\s*\(.\+\)\s*)|\1|;s|['\"]||g")"; \
 	 rm -f "$${grub_dirname:-/boot/grub}/grub-btrfs.cfg"
 	@rm -f "$(DESTDIR)/etc/default/grub-btrfs/config"

README.md

@@ -1,15 +1,15 @@
 [![GitHub release](https://img.shields.io/github/release/Antynea/grub-btrfs.svg)](https://github.com/Antynea/grub-btrfs/releases)
 ![](https://img.shields.io/github/license/Antynea/grub-btrfs.svg)
 
-## grub-btrfs
+## grub-btrfs 
 
 This is a version 4.xx of grub-btrfs
 ##### BTC donation address: `1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt`
-##
-### Description
+- - -
+### Description :
 Improves Grub by adding "btrfs snapshots" to the Grub menu.
 
-You can start your system on a "snapshot" from the Grub menu.  
+You can boot your system on a "snapshot" from the Grub menu.  
 Supports manual snapshots, snapper, timeshift ...
 
 ##### Warning: booting on read-only snapshots can be tricky
@@ -21,7 +21,7 @@ See [this ticket](https://github.com/Antynea/grub-btrfs/issues/92) for more info
 This project includes its own solution.  
 Refer to the [documentation](https://github.com/Antynea/grub-btrfs/blob/master/initramfs/readme.md).
 
-##
+- - -
 ### What does grub-btrfs v4.xx do :
 * Automatically List snapshots existing on root partition (btrfs).
 * Automatically Detect if "/boot" is in separate partition.
@@ -30,50 +30,114 @@ Refer to the [documentation](https://github.com/Antynea/grub-btrfs/blob/master/i
 * Automatically detect snapper and use snapper's snapshot description if available.
 * Automatically generate `grub.cfg` if you use the provided systemd service.
 
-##
+- - -
 ### Installation :
 #### Arch Linux
-
+The package is available in the community repository [grub-btrfs](https://archlinux.org/packages/community/any/grub-btrfs/)
 ```
 pacman -S grub-btrfs
 ```
 
+#### Gentoo
+grub-btrfs is only available in the Gentoo User Repository (GURU) and not in the official Gentoo repository.  
+If you have not activated the GURU yet, do so by running:
+```
+emerge -av app-eselect/eselect-repository 
+eselect repository enable guru 
+emerge --sync 
+```
+
+Now merge grub-btrfs via 
+`emerge app-backup/grub-btrfs`
+
 #### Manual
 
 * Run `make install` or look into Makefile for instructions on where to put each file.
+* Dependencies:
+  * [btrfs-progs](https://archlinux.org/packages/core/x86_64/btrfs-progs/)
+  * [grub](https://archlinux.org/packages/core/x86_64/grub/)
 
-NOTE: Generate your Grub menu after installation for the changes to take effect.  
-On Arch Linux use `grub-mkconfig -o /boot/grub/grub.cfg`.
-
-##
-### Customization:
+#### NOTE: All distros
+Generate your Grub menu after installation for the changes to take effect.  
+For example:  
+On **Arch Linux** or **Gentoo** use `grub-mkconfig -o /boot/grub/grub.cfg`.  
+On **Fedora** use `grub2-mkconfig -o /boot/grub2/grub.cfg`  
+On **Debian-like** distribution `update-grub` is an alias to `grub-mkconfig ...`
+- - -
+### Customization :
 
 You have the possibility to modify many parameters in `/etc/default/grub-btrfs/config`.  
 See [config file](https://github.com/Antynea/grub-btrfs/blob/master/config) for more information.
 
-##
-### Automatically update grub
-If you would like Grub to automatically update when a snapshot is made or deleted:
-* Use `systemctl start/enable grub-btrfs.path`.
-* `grub-btrfs.path` automatically (re)generates `grub.cfg` when a modification appears in `/.snapshots` folder (by default).
-* If your snapshots aren't mounted in `/.snapshots`, you must modify the watch folder using `systemctl edit grub-btrfs.path`.  
-	* For example: Timeshift mount its snapshots in `/run/timeshift/backup/timeshift-btrfs/snapshots` folder.
+- - -
+### Automatically update grub :
+#### Systemd
+1. If you would like grub-btrfs menu to automatically update when a snapshot is created or deleted:
+* Use `systemctl enable grub-btrfs.path`.
+  * `grub-btrfs.path` automatically (re)generates `grub-btrfs.cfg` when a modification appears in `/.snapshots` mount point (by default).
+  * If the `/.snapshots` mount point is already mounted, then use `systemctl start grub-btrfs.path` to start monitoring.  
+    Otherwise, the unit will automatically start monitoring when the mount point will be available.
+* If your snapshots location aren't mounted in `/.snapshots`, you must modify `grub-btrfs.path` unit using  
+`systemctl edit --full grub-btrfs.path` and run `systemctl reenable grub-btrfs.path` for changes take effect.  
+To find out the name of the `.mount` unit  
+use `systemctl list-units -t mount`.  
+	* For example: Timeshift mounts its snapshot folder in `/run/timeshift/backup/timeshift-btrfs/snapshots`.
 
-		Use `systemctl edit grub-btrfs.path`.
-		Then wrote:
+		Use `systemctl edit --full grub-btrfs.path`.
+		Then replace the whole block by:
 		```
+		[Unit]
+		Description=Monitors for new snapshots
+		DefaultDependencies=no
+		Requires=run-timeshift-backup.mount
+		After=run-timeshift-backup.mount
+		BindsTo=run-timeshift-backup.mount
+
 		[Path]
 		PathModified=/run/timeshift/backup/timeshift-btrfs/snapshots
+
+		[Install]
+		WantedBy=run-timeshift-backup.mount
 		```
-		and finally save.
+		Then save and finally run `systemctl reenable grub-btrfs.path` for changes take effect.  
+		Optional:  
+		If the `/run/timeshift/backup/timeshift-btrfs/snapshots` mount point is already mounted,  
+		then use `systemctl start grub-btrfs.path` to start monitoring.  
+		Otherwise, the unit will automatically start monitoring when the mount point will be available.  
 	* You can view your change to `systemctl cat grub-btrfs.path`.
 	* To revert change use `systemctl revert grub-btrfs.path`.
-##### Warning:
+
+2. If you would like grub-btrfs menu to automatically update on system restart/shutdown:  
+[Look at this comment](https://github.com/Antynea/grub-btrfs/issues/138#issuecomment-766918328)  
+Currently not implemented
+##
+#### OpenRC
+* There is sadly no similar solution to the systemd service yet.  
+As a workaround it is possible to add a script to `/etc/local.d` to execute the snapshot menu update every time you shut down your system.  
+To do so just add the following script as `/etc/local.d/grub-btrfs-update.stop`
+	```
+	#!/bin/bash
+	
+	description="Update the grub btrfs snapshots menu"
+	name="grub-btrfs-update"
+	
+	depend()
+	{
+	  use localmount
+	}
+	
+	bash -c 'if [ -s "${GRUB_BTRFS_GRUB_DIRNAME:-/boot/grub}/grub-btrfs.cfg" ]; then /etc/grub.d/41_snapshots-btrfs; else {GRUB_BTRFS_MKCONFIG:-grub-mkconfig} -o {GRUB_BTRFS_GRUB_DIRNAME:-/boot/grub}/grub.cfg; fi' 
+	```
+	
+	If you want to run the menu update on startup instead, rename the file to `grub-btrfs-update.start`
+
+##### Warning :
 by default, `grub-mkconfig` command is used.  
 Might be `grub2-mkconfig` on some systems (Fedora ...).   
 Edit `GRUB_BTRFS_MKCONFIG` variable in `/etc/default/grub-btrfs/config` file to reflect this.
-##
+- - -
 ### Special thanks for assistance and contributions
-* [maximbaz](https://github.com/maximbaz)
+* [Maxim Baz](https://github.com/maximbaz)
+* [Schievel1](https://github.com/Antynea/grub-btrfs/discussions/173#discussioncomment-1438790)
 * [All contributors](https://github.com/Antynea/grub-btrfs/graphs/contributors)
-##
+- - -

config

@@ -74,6 +74,15 @@ GRUB_BTRFS_IGNORE_SPECIFIC_PATH=("@")
 # Default: ("var/lib/docker" "@var/lib/docker" "@/var/lib/docker")
 GRUB_BTRFS_IGNORE_PREFIX_PATH=("var/lib/docker" "@var/lib/docker" "@/var/lib/docker")
 
+# Ignore specific type of snapper's snapshot during run "grub-mkconfig".
+# Type = single, pre, post.
+# Default: ("")
+GRUB_BTRFS_IGNORE_SNAPPER_TYPE=("")
+
+# Ignore specific description of snapper's snapshot during run "grub-mkconfig".
+# Default: ("")
+GRUB_BTRFS_IGNORE_SNAPPER_DESCRIPTION=("")
+
 # By default "grub-btrfs" automatically detects your boot partition,
 # either located at the system root or on a separate partition,
 # but cannot detect if it is in a subvolume.

grub-btrfs.path

@@ -1,8 +1,12 @@
 [Unit]
 Description=Monitors for new snapshots
+DefaultDependencies=no
+Requires=\x2esnapshots.mount
+After=\x2esnapshots.mount
+BindsTo=\x2esnapshots.mount
 
 [Path]
 PathModified=/.snapshots
 
 [Install]
-WantedBy=multi-user.target
+WantedBy=\x2esnapshots.mount